It's standard business practice. The acquiring company doesn't want to lay off all these people they are inheriting- too much administrative cost on them. It is much better to not have to inherit the problem people in the first place.
So give them limited pay rises. If they leave, good that means we don't have to sack them.
If they stay, good it means we don't have to pay them as much until we sack them.
It's just standard operating procedure for a company takeover.